全文获取类型
收费全文 | 183895篇 |
免费 | 11164篇 |
国内免费 | 10080篇 |
专业分类
电工技术 | 8379篇 |
技术理论 | 70篇 |
综合类 | 17293篇 |
化学工业 | 15457篇 |
金属工艺 | 6123篇 |
机械仪表 | 16244篇 |
建筑科学 | 43256篇 |
矿业工程 | 6002篇 |
能源动力 | 4613篇 |
轻工业 | 5633篇 |
水利工程 | 8578篇 |
石油天然气 | 19776篇 |
武器工业 | 2119篇 |
无线电 | 9441篇 |
一般工业技术 | 16764篇 |
冶金工业 | 3794篇 |
原子能技术 | 796篇 |
自动化技术 | 20801篇 |
出版年
2024年 | 539篇 |
2023年 | 1933篇 |
2022年 | 3241篇 |
2021年 | 4319篇 |
2020年 | 4554篇 |
2019年 | 3522篇 |
2018年 | 3392篇 |
2017年 | 4263篇 |
2016年 | 5116篇 |
2015年 | 5379篇 |
2014年 | 13480篇 |
2013年 | 10413篇 |
2012年 | 13049篇 |
2011年 | 14170篇 |
2010年 | 11706篇 |
2009年 | 12006篇 |
2008年 | 11063篇 |
2007年 | 13260篇 |
2006年 | 11744篇 |
2005年 | 10435篇 |
2004年 | 8695篇 |
2003年 | 7798篇 |
2002年 | 6084篇 |
2001年 | 4957篇 |
2000年 | 4048篇 |
1999年 | 3153篇 |
1998年 | 2507篇 |
1997年 | 2120篇 |
1996年 | 1768篇 |
1995年 | 1424篇 |
1994年 | 1187篇 |
1993年 | 787篇 |
1992年 | 645篇 |
1991年 | 499篇 |
1990年 | 339篇 |
1989年 | 316篇 |
1988年 | 226篇 |
1987年 | 160篇 |
1986年 | 98篇 |
1985年 | 113篇 |
1984年 | 148篇 |
1983年 | 95篇 |
1982年 | 104篇 |
1981年 | 48篇 |
1980年 | 57篇 |
1979年 | 35篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1959年 | 11篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
81.
如今我国信息化技术全面发展,尤其对于工程测量工作领域来讲,不管是在工程建设和管理方面都产生不小的支撑引导效用。由此,笔者具体结合如今工程建设信息化测绘核心任何以及设备布置细节,进行结构整体安全管理周期和周边地理空间信息技术发展能效整理解析,试图将工程测量最新发展机遇和技术挑战问题处理完全。希望能够借此为日后一定时期范围内相关工程测量规划主体提供合理指导性建议内容,最终为我国各类工程事业可持续发展前景绽放奠定深刻适应基础。 相似文献
82.
通过对大直径平底负压容器平底板的设计计算,平底板计算厚度很厚。通过分析,提出了对平底板采取加强措施,从而减薄平底板计算厚度的方法。该容器在实际生产过程中性能可靠、稳定,对类似设备设计具有借鉴意义。 相似文献
83.
This work is concerned with the prediction of visual colour difference between pairs of palettes. In this study, the palettes contained five colours arranged in a horizontal row. A total of 95 pairs of palettes were rated for visual difference by 20 participants. The colour difference between the palettes was predicted using two algorithms, each based on one of six colour-difference formulae. The best performance (r2 = 0.86 and STRESS = 16.9) was obtained using the minimum colour-difference algorithm (MICDM) using the CIEDE2000 equation with a lightness weighing of 2. There was some evidence that the order (or arrangement) of the colours in the palettes was a factor affecting the visual colour differences although the MICDM algorithm does not take order into account. Application of this algorithm is intended for digital design workflows where colour palettes are generated automatically using machine learning and for comparing palettes obtained from psychophysical studies to explore, for example, the effect of culture, age, or gender on colour associations. 相似文献
84.
Dr. Manuel Nieto-Domínguez Dr. Pablo I. Nikel 《Chembiochem : a European journal of chemical biology》2020,21(18):2551-2571
The diversity of life relies on a handful of chemical elements (carbon, oxygen, hydrogen, nitrogen, sulfur and phosphorus) as part of essential building blocks; some other atoms are needed to a lesser extent, but most of the remaining elements are excluded from biology. This circumstance limits the scope of biochemical reactions in extant metabolism – yet it offers a phenomenal playground for synthetic biology. Xenobiology aims to bring novel bricks to life that could be exploited for (xeno)metabolite synthesis. In particular, the assembly of novel pathways engineered to handle nonbiological elements (neometabolism) will broaden chemical space beyond the reach of natural evolution. In this review, xeno-elements that could be blended into nature's biosynthetic portfolio are discussed together with their physicochemical properties and tools and strategies to incorporate them into biochemistry. We argue that current bioproduction methods can be revolutionized by bridging xenobiology and neometabolism for the synthesis of new-to-nature molecules, such as organohalides. 相似文献
85.
The solvent-dependent polymorphism of the active pharmaceutical ingredient (API) carbamazepine is interpreted from calculations of the solid-state and API-solvent intermolecular interactions. These simulations suggested that apolar solute-solute interactions could be disrupted by apolar solvents. In contrast, the polar solute-solute interactions were found to be easily disrupted by polar and protic solvents. This is consistent with experimental observations that the crystallization of the metastable form II is more dominant in apolar solvents. The Mercury program remains the gold standard in terms of usability; however, further expansion into more complex simulation techniques could make this package of even greater use in pharmaceutical manufacturing workflows. 相似文献
86.
C. Busuioc C.D. Ghitulica A. Stoica M. Stroescu G. Voicu V. Ionita L. Averous S.I. Jinga 《Ceramics International》2018,44(8):9433-9441
Bacterial cellulose membranes were employed as templates for calcium phosphates deposition by successive immersion in solutions of Ca(NO3)2·4H2O and (NH4)2HPO4, under ultrasonication. During the wet chemical reaction, mineral phases were loaded on bacterial cellulose fibrils, leading to precursor hybrid composites. These were subjected to a lyophilisation procedure in order to preserve the 3D porous aspect and afterwards to a thermal treatment with the aim of removing the polymeric phase and generating well crystallized structures. Different types of morphologies were achieved by varying the heating rate, as well as the calcination temperature and period. The as-prepared samples and the final ones were investigated from compositional and structural point of view through X-ray diffraction and Fourier-transform infrared spectroscopy and morphologically concerning by scanning electron microscopy. The magnetic properties were also evaluated in order to demonstrate the suitability of the obtained materials for the development of magnetic scaffolds dedicated to hard tissue applications. 相似文献
87.
88.
Kinetic,thermodynamic parameters and in vitro digestion of tannase from Aspergillus tamarii URM 7115
Amanda Reges de Sena Tonny Cley Campos Leite Talita Camila Evaristo da Silva Nascimento Anna Carolina da Silva Catiane S. Souza Antônio Fernando de Mello Vaz 《Chemical Engineering Communications》2018,205(10):1415-1431
Tannase is an enzyme used in various industries and produced by a large number of microorganisms. The aim of this study was to evaluate tannase production to determine the biochemical, kinetic, and thermodynamic properties and to simulate tannase in vitro digestion. The tannase-producing fungal strain was isolated from “jamun” leaves and identified as Aspergillus tamarii. Temperature at 26°C for 67?h was the best combination for maximum tannase activity (6.35-fold; initial activity in Plackett–Burman design—15.53?U/mL and average final activity in Doehlert design—98.68?U/mL). The crude extract of tannase was optimally active at 40°C, pH 5.5 and 6.5. Moreover, tannase was stimulated by Na+, Ca2+, Mg2+, and Mn2+. The half-life at 40°C lasted 247.55?min. The free energy of Gibbs, enthalpy, and entropy, at 40°C, was 81.47, 16.85, and ?0.21?kJ/mol?·?K, respectively. After total digestion, 123.95% of the original activity was retained. Results suggested that tannase from A. tamarii URM 7115 is an enzyme of interest for industrial applications, such as gallic acid production, additive for feed industry, and for beverage manufacturing, due to its catalytic and thermodynamic properties. 相似文献
89.
筒形阀是一种新型的水轮机进水阀,它与球阀或蝴蝶阀相比较有防止机组飞逸事故扩大效果明显、减轻导叶全关时导水机构的快速破坏并减少漏水量,以及动水开启方便、所需时间短等优点,但对运行条件也有一定的要求。光照水电站是贵州省第1个拟采用筒形阀的电站,为此对装设筒形阀的可行性和必要性进行了认真的分析。 相似文献
90.